Forming tools fabricated from composites have several advantages over forming tools made from more traditional materials, such as wood or metals. First, the composite forming tools are lightweight and more easily handleable. Second, and more importantly, the composite forming tools provide a match for the thermal expansion of the composite article being produced during the high temperature curing cycle. This improves the dimensional accuracy of the articles produced by the forming tool.
Fabrication of composite structure such as the composite forming tools can be a time consuming and expensive process. The current method consists of creating a master model, from wood or some other shapeable material, of the article to be produced. The master model is then used to fabricate working masters made from composite material through an intermediary process involving the use of tooling splashes made from castable material capable of withstanding the high temperatures required during the curing process. The working master is then used to fabricate the forming tool. Due to the additive nature of the tolerances involved in each step, the dimensional accuracy of the composite forming tool and therefore the article produced is significantly reduced.
An alternative method for fabricating composite forming tools was disclosed in Kundinger et al, U.S. Pat. No. 4,578,303. This method involved the use of a lattice support structure made from composite materials. Each rib or header is cut to the shape desired and the series of ribs produce the contoured surface desired for the forming tool. Several layers of laminate are placed over and bonded to the support structure during curing of the forming tool. While this method has advantages over the current method described above, it has several drawbacks which limit its use. The first is the time intensive process of cutting each of the support ribs. A second drawback is the additional weight due to using a lattice support structure. Additionally, to avoid dimpling of the layers of laminates during the curing process the ribs would have to be tightly spaced, a characteristic which multiplies the number of ribs necessary and thereby increases the weight of the tool.